Segments and Related Information (Schedule of Financial Information by Reportable Segment - Revenue) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue:
Revenue (in dollars)		$ 1,586,181	$ 1,111,010	$ 3,792,811	$ 3,180,906
Communications [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Utilities [Member]
Revenue:
Utilities customers, percentage of Communications segment revenue		11.10%	11.20%	10.90%	10.50%
Reportable Segments [Member] | Communications [Member]
Revenue:
Revenue (in dollars)	[1]	$ 624,300	$ 513,300	$ 1,728,000	$ 1,452,100
Reportable Segments [Member] | Oil and Gas [Member]
Revenue:
Revenue (in dollars)		736,000	406,900	1,454,300	1,144,200
Reportable Segments [Member] | Electrical Transmission [Member]
Revenue:
Revenue (in dollars)		101,700	75,900	283,600	270,200
Reportable Segments [Member] | Power Generation and Industrial [Member]
Revenue:
Revenue (in dollars)		123,600	115,000	324,700	302,300
Reportable Segments [Member] | Other [Member]
Revenue:
Revenue (in dollars)		7,600	3,800	14,900	17,200
Eliminations [Member]
Revenue:
Revenue (in dollars)		$ (7,000)	$ (3,900)	$ (12,700)	$ (5,100)

[1] Revenue generated primarily by utilities customers represented 11.1% and 11.2% of Communications segment revenue for the three month periods ended September 30, 2016 and 2015, respectively, and represented 10.9% and 10.5% for the nine month periods ended September 30, 2016 and 2015, respectively.